The present invention relates to an arrangement for a hydraulic brake booster including a booster chamber permitting the controlled delivery of fluid thereto from an auxiliary source of pressure-transmitting fluid, wherein the auxiliary source is a pump supplying a pump-circulated fluid to be throttled by a throttle element, and the throttle element is actuatable by the pressure in the booster chamber in addition to being loaded by a weak spring, and wherein an arrangement is provided for limiting the maximum amount of pressure that can be throttled. Such an arrangement is known from German Pat. No. DE-AS 2,360,133.
In the known arrangement, the throttle element is directly acted upon in the actuating direction by the pressure prevailing in the booster chamber, and the action of the weak spring causes continuous throttling of a predetermined pressure in the pump-circulated fluid, which pressure is somewhat higher than the pressure in the booster chamber. As a result, when the brake pedal is depressed vehemently, an ever increasing pressure can be built up in the booster chamber which is ultimately limited to a maximum value by the added provision of a pressure-limiting valve in order to avoid damage to the brake system. It is a disadvantage in this known arrangement that the necessary pressure-limiting valve requires a relatively complicated construction. Further, the control movements of the throttle element are transmitted to the booster chamber as a result of the direct hydraulic application, because for the throttle element to be acted upon by pressure it is necessary to feed or withdraw low quantities of fluid continuously. This causes vibrations in the booster chamber which may resonate and, thus, disturb the braking action substantially.